This invention relates to in-vitro diagnostic method by radioimmunoassay for the detection of acetylsalicylic acid ingestion by a patient. In particular, the unique method is designed to detect antibodies elicited in the patient's serum responsive to salicylate ingestion.
Acetylsalicylic acid, commonly known as aspirin, is perhaps the most prevalent drug used by the general population to alleviate symptoms of a wide variety of illnesses. However, in recent years, it has been recognized by medical practitioners that there exists a possibility of long-term toxic effects from ingestion of the drug. For example, analgesic nephropathy is one such deleterious effect reported by Spuhler, O. and Zollinger, H. in Helv. Med. Acta, 1950, 17, 564.
Moreover, adverse effects of salicylate ingestion, notably, changes in epithelial-cell excretion rate, tubular handling of electrolyte, acidification, and enzyme excretion have also been studied.
Kimberly and Plotz, in P.H. New England Journal of Medicine 1977, 296, 418, hypothesized that the cause of functional abnormalities from salicylate ingestion is the suppression of prostaglandin synthetase with consequent fall-off in renal profusion.
Remuzzi, G. et al. in "The Lancet", Aug. 13, 1977 at page 359 et seq. have recognized that aspirin should be withheld from patients with chronic renal failure, since it may cause a further decline in renal function and could carry an increased risk of gastrointestinal haemorrhage.
Collins, E. and Turner, G. in "The Lancet", Oct. 9, 1976 at page 797 et seq. report that very few daily takers of aspirin disclosed this information to their physicians during antenatal visits, and many denied taking aspirin--containing powders at the beginning of a postnatal interview until told that they had had salicylate in their urine at every antenatal visit. The purpose of such questioning was to confirm the deleterious effects of apsirin which occur mainly during the last trimester of pregnancy. One such effect was a relatively high still-birth rate found in the study which was speculated to be caused by salicylate on platelet function.
The techniques of solid-phase RIA of antigens or antibodies are generally known in the art. However, they have not been applied to a system for detecting ASA ingestion. U.S. Pat. No. Re 29,955 to Bornstein et al and U.S. Pat. No. 3,790,663 to Garrison et al., indicate that solid-phase RIA was introduced to the art by Catt and co-workers. The Catt technique involves the bonding of antibodies to a polymeric solid-phase. Accordingly, the bonded antiserum is utilized to selectively bind antigen for which the antiserum is specific. When radioactively labelled antigen is added to the sample being assayed, such as blood or serum, the labelled and unlabelled antigen compete for binding by the antiserum. The more unlabelled antigen competing for the aniserum binding sites the less labelled antigen will be found. Thus, by incubating the coated solid-phase with a specimen to which radioactive labelled antigen has been added and then counting the radiation content of the solid-phase, the antigen concentration of the specimen can be determined. Specific techniques for solid-phase polymers in the RIA field have been reported in Biochem. J. 100: 31C (1966), Science, 158: 1570 (1967) and J. Lab & Clin. Med., 70: 820 (1967) as well as other reported journal articles and patents.
While RIA as applied to general diagnostic methods has been known, the procedure for the assay of antibodies elicited from acetylsalicylic acid ingestion in accordance with the present invention has not. On possible reason for the apparent lack of application is that much of the acetylsalicylic acid ingested is destroyed in the patient's digestive tract with a consequent minute quantity of antibodies produced.
Accordingly, those skilled in the art, have recognized a significant need for a sensitive in-vitro diagnostic method for detecting such ingestion, particularly when the patient is unwilling or unable to convey this critical information to a treating physician.
The present invention fulfills these needs.